docs: refresh dashboard screenshot with live MacBook v0.5.1 data (#60)

D82 originally rendered docs/img/dashboard-v0.5.0.png from synthetic
quota_v2 data (the live API wasn't probed at the time of capture).
After v0.5.1 hotfix shipped, the screenshot is replaced with a render
from a real /v0/management/dashboard-data response captured 2026-05-27
from the MacBook OLP server on commit fa2d1af (F4+#7 post-merge).

Changes:
- docs/img/dashboard-v0.5.0.png → docs/img/dashboard-v0.5.1.png
  (rename + content refresh; new content is the v0.5.1 live capture)
- README.md screenshot reference updated to v0.5.1 path + alt-text
  now includes the live utilization numbers (5h: 6%, 7d: 38%)
- docs/exit-gates/phase-5-e2e.json refreshed to reflect the post-v0.5.1
  test (different server version, different temp owner key, new
  utilization snapshot). Records the v0.5.1 contract verifications
  (status enum, failure null for healthy live, schema_version match).

Post-test cleanup verified:
- Temp owner key (id=0m6s2s97, name=v0.5.1-screenshot) revoked
- ~/.olp/config.json providers.anthropic.quota_probe_enabled flag
  removed (config restored to baseline)
- Test server (port 14567) terminated

No code or contract changes. Pure documentation refresh.

Co-authored-by: dtzp555 <dtzp555@gmail.com>
Co-authored-by: Claude Opus 4.7 <noreply@anthropic.com>

README.md

@@ -283,7 +283,7 @@ See [ADR 0004 (Fallback Engine)](./docs/adr/0004-fallback-engine.md), [ADR 0007
 
 OLP v0.5.0+ surfaces live subscription quota for Anthropic Pro/Max subscribers on the owner-only `/dashboard`. Per-provider rows show 5-hour and 7-day utilization bars with reset countdowns, status badges, representative-claim hints, and a manual refresh button. The panel auto-refreshes every 60 seconds and pauses when the tab is hidden.
 
-![OLP v0.5.0 dashboard — Plan Usage panel with live anthropic quota](./docs/img/dashboard-v0.5.0.png)
+![OLP v0.5.1 dashboard — Plan Usage panel with live anthropic quota (utilization 5h: 6%, 7d: 38%, status: live)](./docs/img/dashboard-v0.5.1.png)
 
 ### How it works